[libvirt] [RFC] Design executing commands from within domains

[Chen Hanxiao]

At 2016-08-08 23:00:38, "Michal Privoznik" <mprivozn at redhat.com> wrote:
>Dear list,
>
>while wiring qemu-ga into libvirt I've noticed that it has ability to
>spawn commands inside guest. I haven't paid much attention to it then as
>implementing libvirt <-> qemu-ga communication was more important. But
>lately couple of requests on the list showed up where ability to spawn
>various commands inside guests would be much appreciated (e.g. when
>fetching some stats that HV can't know or has no support for yet -
>free/df/..).
>
>When it comes to spawning commands we distinguish two modes: sync and
>async. I think we should stick to this on the public API level too. Yet
>better, we can have async APIs and the sync API would just be a wrapper
>around async then.
>

Cool!
We should had a API than using qemu monitor command.

...

>virStreamEventAddCallback(st, VIR_STREAM_EVENT_READABLE,
>domainCommandCallback, ...);
>
>/* ... */
>
>virDomainCommandJoin(dom, cmd);
>
>virStreamEventRemoveCallback(con->st)
>
>virDomainCommandFree(cmd);
>

Do we had timeout mechanism?
Some command may hang for a long time in guest.

Regards,
- Chen

>
>
>While qemu-ga can handle input for a binary its executing, this must be
>put right into JSON when constructing the qemu-ga command. It's not
>common that by that time users know the input they want to enter. So I
>have to figure out something.
>
>Opinions?
>
>Michal
>
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